Laminated article

ABSTRACT

Hydrogenated boron-silica alloy films having unexpected properties permitting in one embodiment the bonding together of metal and ceramic substrates by coating the surfaces to be bonded with the film mating the surfaces and heat treating the mated surfaces to expell hydrogen therefrom and to react to resulting boron-silicon alloy film with the substrates to form a liquid reaction product which forms a surface bond with the substrates or is at least partially absorbed in the substrates. In another embodiment, at least one surface of an intermetallic compound formed from elements selected from groups III and V of the periodic table is sealed against structural degradation by forming on the surface a solid boron-silicon-hydrogen alloy film. In still another embodiment, metal and organic resin substrates are protected against attack by water vapor, dissociated oxygen and molecular oxygen by forming a solid boron-silicon-hydrogen alloy film on the substrates. The metal substrates are further protected against deterioration by the effects of the recombination of dissociated oxygen and nitrogen by converting the solid boron-silicon-hydrogen alloy film to solid boron-silicon oxide film.

This application is a division of copending application serial number747,635, filed on 6/24/85.

TECHNICAL FIELD

This invention relates to hydrogenated boron-silicon alloy films havingunexpected properties permitting the bonding together of various metaland ceramic substrates, the protecting of various metal and organicresin substrates against attack by atmospheres containing dissociatedoxygen, molecular oxygen, water vapor and dissociated oxygen andnitrogen, and the sealing and stabilizing of intermetallic compoundsagainst structural degradation.

BACKGROUND ART

Solid amorphous silicon-boron-hydrogen alloy films have heretofore beenutilized as electronic materials; see, "Fundamentals of Solar Cells",chapter 1 section 2, Alan L. Fahrenbruch and Richard H. Bube, AcademicPress 1983. Most commonly they are used in the form of deposits,prepared by radio frequency glow discharge decomposition of hydrides, insolid state devices converting solar radiation to electrical energy.Preparation and electrical current-voltage characteristics ofsemiconductor junctions made of thin films of amorphous silicon dopedwith trace amounts of boron are described by W. E. Spear, P. G. LeComber, S. Kinmond and M. H. Brodsky, "Amorphous Silicon p-n Junction",Applied Physics Letters, Vol. 28, No. 2, pg. 105, Jan. 1976. In thiswork, the fact that materials prepared by decomposing the hydride gasesalways contain hydrogen, and the role that this hydrogen plays informing the amorphous structure advantageous for electronicapplications, were not considered. Hydrogen content and bondingconfigurations and their influence on growth and structure of amorphoussilicon films prepared by decomposition of silane have been examined byJ. C. Knights, "Growth Morphology and Defects in Plasma-Deposited a-SI:H Films", Journal of Non-Crystalline Solids, Vol. 35 & 36 (1980), pages159-170.

The high efficiency of solar cells incorporating thin films ofhydrogen-containing amorphous silicon-boron has motivated scientificinterest in the solid state physical properties of compositionsexceeding in boron content the low concentrations utilized forsemiconductors. For example, C. C. Tsai in an article entitled"Characterization of Amorphous Semiconducting Silicon-Boron AlloysPrepared by Plasma Decomposition" published in Physical Reviews, Volume19, page 2041, February 1979, describes structure, optical absorption,electrical conductivity and paramagnetic resonance of hydrogenatedboron-silicon alloys, ranging in composition from 0 to 100% boron. Inthis work, films deposited by glow discharge decomposition of Si H₄ +B₂H₆ gas mixtures on a variety of substrates, including glass, aluminum,crystalline silicon, and saphire have been studied. The relativeefficiency of incorporation of boron from the gas into the film,compared to that of the silicon, is about 0.65+or -0.15 at 270° C.deposition temperature. Therefore, amorphous hydrogenated silicon-boronalloys with any composition in the binary system can be made by properlychoosing the Si H₄ -B₂ H₆ gas mixture. The hydrogen content in the filmshas been found to range between 10 and 45 atomic percent depending onthe deposition parameters. In the film structure, hydrogen forms B--Hand Si--H bonds which represent the majority of the amorphous atomiclattice. The structure and stability of the films depend in greatmeasure on the deposition temperature. Films deposited at 270° C. aredense, contain less than 1 atom percent of oxygen and are very stable toexposure to ambient air. They loose their hydrogen when heated to about350° C. to 550° C. In contrast, films deposited at 25° C. are porous,easily oxidize upon exposure to air, and start losing their hydrogennear 350° C.

In the current electronic art, also pyrolysis, or thermal decomposition,of gaseous hydrides is practiced for preparation of amorphoushydrogen-containing silicon and boron films. An example is the work ofB. G. Bagley, D. E. Aspnes, A. C. Adams and R. E. Benenson described inthe paper entitled "Optical Properties of LPCVD aB(H)" published in theJournal of Non-Crystalline Solids, Vol. 35 & 36 (1980), page 441. Thepaper reports the infra red and near ultra violet absorptions of filmsdeposited on single crystal silicon substrates by pyrolysis of diboraneat temperatures between 290° C. and 400° C. The films have remainedstable upon exposure to laboratory atmosphere for six months without anydegradation by oxidation.

Applicants are unaware of any other uses set forth in the prior art forsilicon-boron-hydrogen alloys. Such alloys have been studied, developedand used exclusively for the purpose of utilizing their physicalbehavior as electronic semiconductors. The only chemical aspects ofthese materials that are recognized by the electronic art are thereactions occurring in the process of their fabrication as solid thinfilms, by decomposition of gaseous silicon and boron hydrides (silanesand boranes). Accordingly, the prior art teaches the composition andpressure of the gases from which the films are formed and the resultingfilm compositions, temperature and rate of their nucleation and growth,atomic lattice structure and stability to temperature and exposure toambient air. The art also implies that the silicon-boron-hydrogen filmscan be deposited on almost any and all known solid substrates includingmetals, ceramics and organic resin materials. However, the art is devoidof any teaching or consideration of the chemical behavior of the filmstowards the substrate on which they have been deposited and towardsmaterials which come in contact with them from the outside.

In the nonanalogous art of joining a specific material to itself or toother materials, a structural transition interface is utilized betweenthe materials. This transition interface is created on atomic andcrystal lattice levels by direct chemical reactions between the twosurfaces in processes such as diffusion or fusion welding or bonding. Inmany instances, for convenience of lower bonding process temperatures,an intermediate filler material is interposed between the two surfacesto interact with each one of them separately and thus bond themtogether. Examples of this kind of state of the art processes are arcwelding, brazing, soldering, and organic adhesive bonding. All thesechemically generated bond interfaces create a region of transition inwhich the interfaced composition and crystalline structures are forcedto adjust to each other. Particularly in the cases of soldering, brazingand adhesive bonding the filler material is retained at the joint andconstitutes an additional adventitious material in the joined assembly.In general, the chemical and physical characteristics of the transitionregion are quite different from those of the bonded materials and poseproblems and disadvantages of dimished mechanical strength, sensitivityto thermal or mechanical shock, or to chemical attack, undesirableelectrical or thermal conductivity, and the like.

Advantages of using boron and/or silicon as active reactants in creatingbonds between metals have been recognized by the current art, as shown,for example, in U.S. Pat. Nos. 2,714,760; 2,868,639; 3,188,203;3,530,568 and 3,678,570. These patents teach joining high temperaturecorrosion and oxidation resistant iron, nickel and cobalt base alloys bymeans of brazing compositions based on nickel-chromium, ornickel-cobalt-chromium, to which boron, or boron and silicon, are added.Boron and/or silicon lower the melting point of the brazes and, thus,the joint can be made at temperatures low enough to avoid deterioratingthe mechanical properties of the bonded alloys. Further advantage ofusing boron and silicon in the brazes is that although they act togenerate a brazing liquid at a conveniently low temperature, they alsoat the same time tend to diffuse out of the bond into the metal andcause the liquid braze bond to solidify. In this way, the remelttemperature of the braze is raised above that of the original brazecomposition and the bonded assembly can be put to use at desirably hightemperatures. However, the use of boron and silicon in this manner doesnot obviate the aforesaid difficulties associated with prior art bondingtechniques.

DISCLOSURE OF INVENTION

Briefly, in accordance with the invention, it has been discovered thatboron-silicon-hydrogen alloys, formed by conventional processes, haveunobvious chemical and structural properties which yield unexpectedresults when applied as surface coatings or films to various metal,ceramic, intermetallic and organic resin substrates.

More particularly, the alloy permit the forming of metal to metal,ceramic to ceramic and metal to ceramic joints, the protection ofmetallic and organic resin substrates against atmospheres containingdissociated or molecular oxygen and nitrogen, oxygen, water vapor andthe sealing of the surfaces of intermetallic compounds formed fromelements selected from groups III and V of the periodic table againststructural degradation.

The bonding of metal and ceramic substrates is accomplished by formingthe solid boron-silicon-hydrogen alloy coating or film on the surfacesto be joined. The film is heated at temperatures sufficient to expellhydrogen from the film and to react the remaining activatedboron-silicon bonds with metal and ceramic substrates to form,respectively, liquid metal-boron-silicon eutectic alloys and liquidborosilicate glasses which chemically interact with the mated surfacesto generate the bond. The chemical interaction might be limited tosurface wetting and involve only superficial layers of the material butin most cases the eutectic alloys and the borosilicate glasses are atleast partially and preferably essentially fully absorbed by thesubstrates. To promote glass formation in the reaction of the boron andsilicon with the ceramic substrates, the heating is done in anatmosphere containing oxygen, such as ambient air. In the case of metalto ceramic bonding, the liquid metal-boron-silicon eutectics arechemically active towards most ceramic surfaces, particularly thosecontaining oxygen. Upon completion of the heat treatment, the liquidphase components and the substrate components adjoining the matedsurfaces have formed chemical bonds at the joint interface and in manycases have at least partially and preferably essentially fully exchangedplaces resulting in a high structural quality joint. The metalsubstrates utilized are those which form with the activatedboron-silicon alloy a liquid ternary metal-boron-silicon eutectic andwhich desirably have at least a limited solubility for boron andsilicon. The ceramic surfaces utilized are those which are able to formin oxygen-containing atmospheres a chemical bond with liquidborosilicate glasses and which desirably have at least a limitedsolubility for boron and silicon oxides.

The chemical stability of the as-formed boron-silicon-hydrogen alloy isthe only property necessary for the sealing of intermetallic compoundsand the protection of metal and organic resin substrates against attackby dissociated oxygen, molecular oxygen and water vapor. No furthertreatments of the film are necessary to achieve these results.

Protection of metal and organic resin substrates against deteriorationby the effects of recombination of dissociated oxygen and nitrogenobtains with the as-deposited boron-silicon-hydrogen coating as well aswith coatings which have been converted to boron-silicon oxides prior toexposure to such atmospheres.

BEST MODE OF CARRYING OUT THE INVENTION

Hydrogen contributes two different chemical properties toboron-silicon-hydrogen films both properties being important toachieving the various utilities of the invention.

For the purposes of protecting and sealing various materials, hydrogenconfers to the films a chemical stability in the temperature range wherethe films retain hydrogen in their composition. For joining and bondingpurposes, expulsion of hydrogen from the films enhances the heretoforeunrecognized chemical reactivity of the films because the boron andsilicon left behind find themselves in a state of unsaturated chemicalbonds and thus activated to find new chemical associations.

In that embodiment of the invention pertaining to the bonding or joiningof materials, the materials are put in contact with each other alongsurfaces coated with a solid boron-silicon-hydrogen alloy film of theinvention. This joint is heated at temperatures sufficient to expellhydrogen from the film and to react the remaining activated boron andsilicon bonds with metal including metal alloy surfaces and ceramicsurfaces to form, respectively, liquid eutectic alloys and liquidborosilicate glasses which form a surface bond with, or are at leastpartially and preferably fully absorbed into the bulk materials.

More particularly, this mechanism involves heating the solid film of theinvention to a temperature at which hydrogen bonds with boron andsilicon are ruptured and hydrogen is expelled from the film. Boron andsilicon then find themselves in a state of unsaturated chemical bondsand thus activated to generate new chemical associations. In particular,the now activated boron and silicon react at readily determinabletemperatures to form liquid phase eutectics with the importantengineering metals and alloys such as aluminum, copper, iron, nickel andcobalt. In similar manner, the activated boron and silicon combine withoxygen in an oxygen-containing atmosphere to form on ceramic substratesborosilicate glasses which are fluid at temperatures considerably lowerthan the melting points of most of the technologically importantceramics.

Therefore, for metal and metal alloy surfaces, the solidboron-silicon-hydrogen alloy film is first converted to a solidboron-silicon alloy film which reacts with the substrate to form aliquid eutectic. A ceramic surface coated with theboron-silicon-hydrogen film is likewise converted to the boron-siliconalloy film which reacts with oxygen at temperatures of formation ofliquid borosilicate glasses.

An optimum bond is ensured when the components of the substrates thatare to be joined diffuse across the bond and merge the two structurestogether. It is well understood by the art that chemical reactions anddiffusion are enhanced in a liquid medium, in this case liquid eutecticsand liquid glasses. The most desirable diffusive reaction occurs forfull dissolution of the liquid eutectic and liquid glass in thesubstrates. The mechanism of dissolution is that of absorbing thedissolving species into the substrate atomic lattice and is connectedwith enhanced atomic movement where the liquid phase components and thesubstrate components exchange places in the crystal lattice. Thismechanism results in a direct bond between the atoms of the twosubstrates while the liquid components are absorbed by dissolution.

The structural quality of joints made by films of the invention ispromoted by the fact that conventional processing of film deposition bychemical absorption from a gas allows for easy control of the depositthickness and, thereby, of the amount of the reactive material whichgenerates the joint. In this way, only the minimum amount necessary toachieve the desired reactions is used. Increasing the film thicknessabove this amount necessitates either higher temperatures or longertimes to promote full dissolution of the liquid components into thesubstrates. Less than full dissolution that is retaining increasingthicknesses of the liquid components between the substrates aftercompletion of processing, increasingly weakens the joint. What is anactual thickness of remaining material excessive for the desired jointis a function of the nature of the joint materials and readilydeterminable by one of ordinary skill in the art.

The invention produces a true integration of the joined materials on theatomic crystalline structure level in the case of metals which arecapable of dissolving in solid solution elemental boron and silicon andin the case of ceramics which are capable of dissolving in theirstructure boron and silicon oxides. The invention is not so limited,however, and has useful applicability to metals and ceramics which havea limited solubility for boron and silicon. For metals, intermetallicboride and silicide compounds are formed by reactions with the liquidphase at the joint interface. In most cases, these compounds tend toremain at the joint location because they are thermodynamically stableand affected very little by the diffusive matter transport mechanism.Similarly, a borosilicate glass bond residue is retained at the jontwith ceramics which have limited tendency of dissolving boron andsilicon oxides in their structure. The influence of these segregationson the structural properties of the joints is restricted, however,because of the small amount of the boron and silicon participating inthe bonding process.

The affinity of boron and silicon towards both metals and oxygen is alsoadvantageous for joining metals to ceramics. Here, the liquidmetal-boron-silicate eutectics are chemically active towards mostceramic substrates, particularly those containing oxygen, and easily wetand bond to the ceramics.

Another novel chemical use of the boron-silicon-hydrogen films of theinvention is for the sealing, that is preserving, the chemical bonds andatomic lattice of surfaces of intermetallic compounds such as galliumarsenide, selected from the compounds formed between elements belongingto groups III and V of the periodic table.

In the process of deposition by decomposition of a borane-silane gasmixture, the deposited solid boron-silicon hydrogenated alloy film bondswith the external, unsaturated chemical valencies at the substratesurface. The film does not disrupt or break the bonds of the underlyingatomic lattice layers of the bulk material. At the depositiontemperature, which is below the hydrogen evolution temperature ofapproximately 350° C., reaction of the film with the diffusion into thebulk material is essentially precluded.

Among the various utilities for this type of surface sealant is its useas an intermediate protective layer when it is necessary to provide onthe intermediate compound surface a layer of another material withoutinterfering with the atomic lattice of the compound. At temperaturebelow formation of liquid phases but above that of hydrogen evolution,the deposited hydrogenated film converts to the solid boron-siliconalloy film which is still effective in protecting the underlyingintermetallic surface.

The chemical stability of the as-formed film is the only propertynecessary for this embodiment of the invention and no further treatmentis necessary to achieve this result.

A further novel chemical use of the hydrogenated films of the inventionis the protection of metallic and organic resin substrates againstharmful attack by atmospheres containing dissociated oxygen, molecularoxygen, water vapor and dissociated oxygen and nitrogen.

Suitable metallic substrates are those containing iron, nickel, cobalt,chromium and aluminum, for example, nickel or iron base high temperaturealloys such as Inconel 617 and MA 956, and titanium. Suitable organicresin substrates are those that do not deteriorate during filmformation, for example, Kapton sold commercially by Dupont.

For applications for protection aganst attack by dissociated oxygen in,for example, the upper earth atmosphere, molecular oxygen and watervapor, the films are used as deposited, needing no furtherthermochemical treatment to accomplish their function. Their as-formedchemical stability is the only property necessary for these embodimentsof the invention.

For protection of metallic substrates against deterioration by theeffects of recombination of dissociated oxygen and nitrogen speciesgenerated, for example, at the surface of a body reentering earthatmosphere, the films are converted to boron-silicon oxides by theatmospheric oxygen under heat generated by friction at the surfaceagainst the atmosphere. The boron-silicon oxygen compound layer soformed is also protective against oxidation of the substrate for alimited amount of time during reentry. For applications where it isnecessary to first form an oxide layer on the surface of the reentrybody or shield to insure it has desirable heat emissivity duringreentry, it is convenient to convert the as-depositedboron-silicon-hydrogen film to boron-silicon oxides by heat treatment inair, for example at 1000° C. for one hour.

The boron-silicon-hydrogen films of the invention are formed byconventional techniques well understood by the art. Illustrative of suchtechniques are the methods used by C. C. Tsai, cited previously, andU.S. Pat. No. 4,064,521. These processes involve subjecting to a glowdischarge a mxture of silicon and boron hydride gases (silane andborane) carried in an inert gas carrier such as argon at a pressurewhich ranges between 0.1 and 10 torrs. Electrons emitted form theelectrodes in the discharge ionize and dissociate the hydride moleculeswhich are attracted to the substrate to form the silicon-boron-hydrogendeposit.

The preferred method of the film deposition for the practice of theinvention is by thermal decomposition of the hydride gases. It is chosenover the glow discharge, or plasma, activated processes generallyutilized by the electronic technology because it is less dependent onthe geometry of the substrate. The glow discharge activation is producedby electrons generated from gases ionized in an electric field createdbetween two electrodes, one of which is, most common, the substrateitself. Therefore, the best results in terms of uniform coverage of thesubstrate surface are secured with flat surfaces directly exposed to thedischarge. Thermal activation, on the other hand, is effected over allthe external substrate surfaces uniformly heated at the processtemperature.

In the preferred method of the invention, the silicon-boron-hydrogenfilms are formed by adsorption on chemically active surface sites ofhydrogen-silicon and hydrogen-boron complex molecules generated bythermal decomposition, at a pressure of 1 atmosphere, of a mixture ofsilane (SiH₄), and diborane (B₂ H₆) gases contained in a hydrogencarrier. At the temperature of the process, which is maintained between200° C. and 350° C., the adsorbed species are mobile and diffuse alongthe surface such that the coverage is independent of the substrategeometry. Since the coating is formed by chemisorption, it becomesbonded only to the atomic, or molecular, layers which physicallyconstitute the surface, and, at the low deposition temperature, it isprevented from forming compounds with, or diffusing into, the substrate.Therefore, the deposition by low temperature chemisorption from a gasmedium accomplishes two purposes important for the embodiments of theinvention: uniformity of coverage independent of the complexity of thesurface geometry and sealing of the substrate surface with a film of ahighly reactive composition.

The deposition is carried out from a flowing stream of the gas fed atatmospheric pressure into a reaction chamber containing the substrateheated to the process temperature which is kept between 200° and 350° C.Below 200° C. the process is slow and produces non uniform powderydeposits, above 350° C. the composition of the film becomes unstable dueto loss of hydrogen. The films best suited for the purposes of theinvention are prepared at about 250° C. Prior to initiating thedeposition, the reaction chamber is evacuated, heated under vacuum tothe process temperature and then purged with pure nitrogen for one hour.After purging, the reactive gas is admitted and kept flowing at thedesired rate for the duration of the treatment. The temperature usuallyrises spontaneously at the beginning for a short time due to theexothermic nature of the adsorption of the first layer of the coating.After that the temperature falls down agains and remains stable whilethe film's thickness increases to its final level. After the film hasattained its full thickness, the reactive gas mixture is replaced withnitrogen, the chamber is cooled down under the flow of nitrogen toambient temperature and the coated substrate is taken out. Due tochemical stability at low temperatures, the storage of as coatedarticles under ambient conditions does not pose aging and deteriorationproblems.

The composition of the gas feed for the film deposition and the durationof the deposition depend on the embodiment of the invention for whichthe film has been prepared. The gas feed is made up of two components: amixture of about 2% silane (SiH₄) and about 98% hydrogen and a mixtureof about 1% diborane (B₂ H₆) and about 99% of hydrogen. These twocomponents are mixed together prior to being admitted to the reactionchamber by feeding them each at a different rate through a mixingflowmeter. For all the above invention embodiments, except for ceramicto ceramic bonding, the optimum flow measured in cubic centimeters perminute has been found to be 15cc of borane-hydrogen mixture and 385cc ofsilane-hydrogen mixture. Conditions for bonding ceramics which requireformation of borosilicate glasses are 105cc of borane-hydrogen and 210ccof silane-hydrogen. The time of treatment for all five embodiments ofthe invention is the same, about 20 minutes. It produces a film between1.0 and 1.5 micrometers thick. This thickness has been foundsatisfactory in all cases.

In preparation for film deposition, the surfaces are cleaned withappropriate commercial solvents or soap solutions to remove impuritiesand grease. Metals are additionally pickled and smut is removed by suchprocedures as normally applied in industrial practice prior to anycoating process.

The most efficient bonding of metals obtains when the bond interface isliquid during the process. Although solid state diffusion bonds can bemade using the films of the invention, they might require excessivelyhigh temperatures and long times. The invention is accordingly bestsuited for those cases where at least one of the materials being joinedis able to react with the film to produce a low-melting phase, i.e.,melting at a temperature low enough not to impair the properties of thematerials during the joining operation. The invention, therefore, ismost advantageous when applied to metals containing in theircompositions such elements as gold, silver, copper, iron, nickel, orcobalt, all of which react with either or both boron and silicon togenerate liquid eutectic phases at temperatures not higher than 1200° C.These metals can be joined to themselves, to each other, to other metalsand to oxide ceramics by depositing on them the film of the invention,putting them in contact with the surface to which they are to be joinedunder a pressure of a few pounds per square inch and heating theassembly to a temperature between 10° C. and 50° C. above the respectiveeutectic temperature in an inert atmosphere, or vacuum, to preventoxidation. The eutectic temperatures of interest are easily found inscientific and technical literature. The time of heating is chosenaccording to the structure expected for the joint. The best procedure isto determine by experiment the structure best suited for each case. Ingeneral, the increase of time at joining temperature will increase thediffusion effects producing dissolution of boron and silicon away fromthe joint interface and grain growth across the bond. The bond betweenceramics using conversion of the boron-silicon-hydrogen films into aborosilicate glass is made by heating the assembled joint in air atillustrative temperatures of about 1200° C. to 1300° C.

To make the joints of the invention, it is not necessary to coat bothsurfaces which are to be bonded together with the boron-silicon-hydrogenfilm. It is sufficient to deposit the film only on one surface. Joiningdifferent materials, it is advantageous to put the film on the materialwhich has the better affinity to react with the film and generate thebond-forming phases such as the liquid eutectic. However, from the pointof view of protecting the surfaces from deteriorating by exposure toambient air prior to making the joint, it is desirable to have both ofthe surfaces coated because the film is an efficient protection againstoxidation, even by humid atmosphere. Several examples are given toillustrate the preparation and characteristics of the hydrogenatedboron-silicon alloy films of the invention.

EXAMPLE 1

Boron-silicon-hydrogen film was used to bond together two pieces of mildsteel (SISI-SAE type 1020). The surfaces were ground flat on a fineemery paper and etched by immersion for 30 seconds in an acid solutioncomposed of 17 volume percent hydrofluoric acid, 44 to 55% concentrated,33 volume percent nitric acid, 70% concentrated, and 50 volume percentdeionized water. After etching, the samples were rinsed in running waterand the oxide smut produced on the surface by the etching was removed byimmersion for 150 seconds in a solution composed of 7.5 volume nitricacid, 70% concentrated, 48 volume percent sulfuric acid, 90% minimumconcentrated, and 44.5 volume percent sulfuric acid, 90% minimumconcentrated, and 44.5 volume percent deionized water. The etched andcleaned samples were rinsed in running water, drained and allowed todry. They were then placed in a reaction chamber which was evacuated,heated under vacuum to a temperature of 250° C. and then purged withpure nitrogen for one hour. The flow of nitrogen was then replaced by aflow of a mixture of two gases, hydrogen containing 2% silane (SiH₄) andhydrogen containing 1% diborane (B₂ H₆). Their flow was adjusted to 15cubic centimeters per minute of the borane-hydrogen gas and 385 cubiccentimeters per minute of the silane-hydrogen gas, giving a total gasmixture flow through the chamber of 400 cubic centimeters per minute.This flow was maintained for 26 minutes after which time it was replacedby a flow of pure nitrogen. The heat source was then shut off and thesamples were allowed to cool down to room temperature under the purenitrogen flow. The coated samples were assembled by mating the coatedsurfaces under a pressure of 10 pounds per square inch and heating at atemperature of 1200° C. in vacuum for 1 hour. The bond generated by thisprocess between the two steel samples was entirely absorbed in thematerial by steel crystals grown across the joint.

EXAMPLE 2

Two pieces of Inconel 617 alloy (22.63% Cr, 12.33% Co, 9.38% Mo, 1.155Al, 0.76% Fe, 0.27% Ti, 0.15% Si, balance Ni) were bonded together usingboron-silicon-hydrogen film coatings deposited on the mating surfaces.The procedure and process parameters applied for film deposition andbonding treatment were identical to those described in Example 1. Alsoin this case, the bond has been entirely absorbed by Inconel crystalsgrown across the joint.

EXAMPLE 3

Two plates of fused quartz glass (pure SiO₂) were bonded together usingboron-silicon-hydrogen film coatings deposited on the mating surfaces.The procedure and processing time and temperature applied for filmdeposition were identical with those described in Example 1 exceptcleaning of the surfaces to be coated was confined to a wash withorganic solvent and the flow of the coating gases through the depositionchamber was adjusted to 105 cubic centimeters per minute of theborane-hydrogen gas and 210 cubic centimeters per minute ofsilane-hydrogen gas, to a total flow of 315 cubic centimeters per minuteof the gas mixture. The coated samples were assembled as described inExample 1 and heated at a temperature of 1250° C. in an air furnace for1 hour. The bond generated between the quartz surfaces was completelyabsorbed in the material. No segregations or voids were found at thejoint.

EXAMPLE 4

Two plates of sintered aluminum oxide (Al₂ O₃) were bonded togetherusing boron-silicon-hydrogen film coatings deposited on the matingsurfaces. The procedure and process parameters applied for filmdeposition and bonding treatment were identical to those described inExample 3. Also in this case, the bond had been absorbed in thematerial. Only traces of borosilicate glass bond remained at the jointinterface in the form of dispersed isolated inclusions.

EXAMPLE 5

Two pieces of sintered silicon carbide (SiC) coated withboron-silicon-hydrogen film were joined together with a 0.003 inch thickaluminum metal foil interposed between the mating surfaces. The matingsurfaces of the silicon carbide pieces were coated with the film usingprocedure and process parameters described in Example 1. The bondbetween the coated silicon carbide surfaces and the aluminum sandwichedbetween them was formed by heating the assembly at 700° C. for one hourin vacuum under a pressure of 10 pounds per square inch. The bond wasuniform and free of structural defects such as voids and foreignmaterial inclusions. Under a shear load, the bond ruptured within thesilicon carbide.

EXAMPLE 6

Structural alloys for thermal protection systems of spacecraftreentering earth atmosphere require on the surface a high emissivityoxide layer with a low catalytic activity to the recombination ofdissociated species, such as atomic oxygen and nitrogen, present in theboundary layer during reentry. Several samples of alloy MA 956 (19.30%Cr, 4.28% Al, 0.49% Y, 0.39% Ti, 0.28% Ni, 0.20% 0, balance Fe) werelightly grit blasted with 120 mesh alumina and oxidized for 2 hours at2000° F. in static air. The oxidized surfaces were then coated withboron-silicon-hydrogen film using the procedure described in Example 1.The coated specimens were again oxidized in air and then exposed in anarc-heated wind tunnel to repeated cyclic tests of 0.5 hour each, undersimulated reentry conditions at surface temperatures ranging from 1500°to 2300° F. Catalytic activity of the sample surfaces was assessed bycomparing the response of coated and uncoated specimens for up to 5.5hours of total exposure to test temperature during cycling. While thesurface catalysis ratio, expressed as the ratio of net aerothermalheating rate and the catalytic wall heating rate, for uncoated MA 956alloy surface was close to 1, that of the coated one was only about 0.5.

EXAMPLE 7

Development of field effect transistor devices using gallium arsenidesemiconductor materials is seriously hindered by difficulty in securinga surface passivation layer which would not interfere with free movementof electrical charges at the interface between the dielectric and thesemiconductor. Hydrogenated boron-silicon film was used as a transitionlayer between GaAs and a silicon oxide passivation to eliminate chargeinjection into the dielectric. Samples of thin wafers of single crystalGaAs were coated with the film using the procedure described inExampel 1. About 0.25 micrometer thick layer of silicon oxide wasdeposited on the top of the film by standard microelectronic artchemical vapor deposition methods. The nature of the interface betweenthe passivation film and the GaAs surface was investigated by slow-sweep10-KHz capacitance-voltage plots. Most of the best quality oxidedielectrics available in the current state of the art display aclockwise hysteresis in the C-V curves which is attributed to chargeinjection into the oxide. The hysteresis, and, therefore, the chargeinjection it indicates, were eliminated in the samples with the siliconoxide dielectric deposited on the top of the hydrogenated boron-siliconfilm.

What is claimed is:
 1. A first and a second substrate material matedtogether, said materials being selected from the group of materialsconsisting of metals and ceramics, and a solid boron-silicon-hydrogenalloy film at the interface between said first and second substratematerial, wherein said film bonding said first and second substratematerial together has been heat treated at a temperature sufficient toconvert said boron-silicon-hydrogen film to solid boron-silicon alloyfilm which reacts with at least one substrate material to form a liquidreaction product which chemically interacts with said material.